Spatiotemporal development of cuticular ridges on the leaf surfaces of Hevea brasiliensis alters insect attachment

Cuticular ridges on plant surfaces can control insect adhesion, wetting behaviour and might also offer stability to underlying cells during growth. Yet, the influence of ontogenetic changes in the morphology of such surface microstructures on interactions of insects with plant organs has been largely neglected. In this study, we present spatial and temporal patterns in cuticular ridge development on the leaf surfaces of the model plant, Hevea brasiliensis. Through confocal laser scanning microscopy of polymer replicas of the leaves, we identified an acropetally directed progression of ridges during the ontogeny of Hevea brasiliensis leaf surfaces. Using Colorado potato beetles (Leptinotarsa decemlineata) as model insect species, we show that the changing dimensions of cuticular ridges on plant leaves during ontogeny have a significant impact on insect traction forces and act as an effective indirect defence mechanism. The traction forces of walking insects were significantly lower on mature leaf surfaces compared to young leaf surfaces, and the measured walking traction forces showed a strong negative correlation with the dimensions of cuticular ridges.